JP4483742B2 - Manufacturing method of EL element - Google Patents

Description

  The present invention relates to a method for manufacturing an EL (electroluminescence) element in which a light emitting layer is sandwiched between a pair of electrodes, and more particularly to improvement in luminance by laser irradiation.

  An EL element is formed by laminating a lower electrode, a light emitting layer made of a phosphor such as zinc sulfide (ZnS), and an upper electrode on a substrate by sputtering or vapor deposition, and usually emits light with each electrode. An insulating layer is interposed between the layers.

  In an EL element having such a structure, a voltage is applied between the upper and lower electrodes to cause the light emitting layer to emit light. In order to improve the light emission luminance, a method of irradiating the light emitting layer with laser light has been proposed. (For example, refer to Patent Document 1).

This device emits light compared to before irradiation by forming a lower electrode and a light emitting layer on a substrate and then irradiating the light emitting layer from the light emitting layer side using a solid laser, excimer laser, etc. The brightness is improved.
JP-A-11-224777

  However, in the laser irradiation method described in Patent Document 1, the light emission layer is directly irradiated with laser light, so that the irradiation energy cannot be made very large. For example, if the irradiation energy exceeds a certain level, problems such as sublimation of the light emitting layer occur, and the range of irradiation conditions for improving the light emission luminance while preventing this sublimation becomes extremely narrow.

  Therefore, the present inventor, after forming the laminated structure of the EL element, that is, after the light emitting layer is sandwiched between a pair of electrodes and performing laser irradiation, the light emitting layer is covered with the electrodes, For example, it was considered that sublimation of the light emitting layer did not occur.

  The present invention has been made in view of the above problems, and in a method for manufacturing an EL element in which a light emitting layer containing a light emitting material is sandwiched between a pair of electrodes, laser irradiation is performed after the light emitting layer is sandwiched between the pair of electrodes. The purpose is to improve the brightness.

  The present inventor has a configuration in which light emission from a light emitting layer is extracted in an EL element in which a light emitting layer containing a light emitting material is sandwiched between a pair of electrodes. Note that laser light can be transmitted.

  Therefore, the first laser beam is applied to the light emitting layer from the one electrode side through which the laser beam can pass to the light emitting layer, and the second laser beam is irradiated to the other electrode side. It was considered that the luminance could be improved by heating the electrode and heat-treating the light-emitting layer by heat conduction from the other electrode to the light-emitting layer.

  For that purpose, the absorption rate of the first laser beam in the light emitting layer and the absorption rate of the second laser beam in the other electrode must be large to some extent, and laser beams of various wavelengths are used. It was thought that the above-mentioned absorption rate in the above was obtained, and the effect of improving the brightness should be investigated.

  The present invention was obtained as a result of experimental studies based on such an idea, and was obtained, and after sandwiching the light emitting layer (13) between the pair of electrodes (11, 15), from one electrode side. The light emitting layer (13) is irradiated with the first laser light (L1) having a wavelength at which the absorption rate of the light emitting layer (13) by a single film is 40% or more, and the other side opposite to one electrode. A process of irradiating the other electrode with the second laser light (L2) having a wavelength of 30% or more of the absorption rate of the other electrode from the electrode side of the other electrode to improve the emission luminance. It is characterized by performing.

  According to this, as shown in FIGS. 5 and 6 to be described later, after sandwiching the light emitting layer (13) between the pair of electrodes (11, 15), the laser irradiation can be performed to improve the luminance.

  Here, when the pair of electrodes (11, 15) are formed of the same material and have different film thicknesses, the thinner electrode is easier to transmit laser light, Since the thicker electrode is easier to absorb the laser beam, the first laser beam (L1) is irradiated from the thinner electrode side, and the second laser beam (L2) is irradiated. Is performed from the thicker electrode side.

  In addition, the code | symbol in the bracket | parenthesis of each means described in the claim and this column is an example which shows a corresponding relationship with the specific means as described in embodiment mentioned later.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the following drawings, parts that are the same or equivalent to each other are given the same reference numerals in the drawings for the sake of simplicity.

(First embodiment)
FIG. 1 is a diagram showing a schematic cross-sectional configuration of an EL element 100 according to the first embodiment of the present invention. The EL element 100 includes an optically transparent first electrode 11, a first insulating layer 12, a light emitting layer 13, a second insulating layer 14, and an optically transparent second electrode on a glass substrate 10 that is an insulating substrate. 15 are sequentially laminated.

  Here, the first electrode 11 and the second electrode 15 are a plurality of electrodes arranged in stripes orthogonal to each other. And when a predetermined voltage is applied to the intersection of the 1st electrode 11 and the 2nd electrode 15, the light emitting layer 13 of the part light-emits. In the case of this EL element 100, light emission of the light emitting layer 13 can be taken out from both sides of the upper and lower electrodes 11 and 15.

  As the glass substrate 10, non-alkali glass or low alkali glass is used, and as the first and second electrodes 11 and 15, an ITO (indium tin oxide) film is used.

As the first and second insulating layers 12 and 14, various transparent insulating films can be used. In this example, Al ₂ is formed by atomic layer deposition (ALD) (Atomic-Layer-Deposition). An O ₃ / TiO ₂ laminated structure film is used. This is a film in which Al ₂ O ₃ and TiO ₂ are alternately laminated.

  The light emitting layer 13 is made of a II-VI group compound semiconductor to which a rare earth element is added. Specifically, ZnS, SrS, CaS is added with Mn, terbium (Tb) or the like as a light emission center. used. In this example, the light emitting layer 13 is made of zinc sulfide: manganese (ZnS: Mn) with ZnS as the base material and Mn added as the emission center.

  Next, a method for manufacturing the EL element 100 of this example will be described. First, an optically transparent ITO film is formed on the glass substrate 10 as the first electrode 11 by a 600 nm sputtering method.

Further, an Al ₂ O ₃ / TiO ₂ laminated structure film is formed as the first insulating layer 12 by the ALD method. Since the ALD method is relatively known, the details are omitted, but specifically, an Al ₂ O ₃ layer is formed using AlCl ₃ and H ₂ O as raw materials, and TiO ₂ is formed using TiCl ₄ and H ₂ O as raw materials. Film formation is performed by alternately repeating the film formation process of forming layers.

Thus, in this example, the Al ₂ O ₃ layer and the TiO ₂ layer have an Al ₂ O ₃ / TiO ₂ laminated structure in which the thickness per layer is 5 nm and the total film thickness is 60 nm. A first insulating layer 12 is formed as a film.

  Then, a 300 nm thick light emitting layer 13 made of ZnS: Mn is formed on the first insulating layer 12 by vapor deposition. Thereafter, the second insulating layer 14 is formed with the same structure and film thickness as the first insulating layer 12, and finally the ITO film having a thickness of 200 nm is formed as the second electrode 15 by the same method as the first electrode 11. Is deposited.

  In this way, a laminated structure of the EL element 100 in which the light emitting layer 13 as shown in FIG. 1 is sandwiched between the pair of electrodes 11 and 15 is completed. This is the element forming process.

  Next, in this example, as a part of the manufacturing process of the EL element, a process of irradiating the element with laser light is performed in order to improve the light emission luminance (laser irradiation process).

  Here, as shown in FIG. 1, while the light emitting layer 13 is sandwiched between the pair of electrodes 11 and 15, the first laser light L1 is irradiated from the second electrode 15 side to the light emitting layer 13, The first electrode 11 is irradiated with the second laser light L2 having a wavelength different from that of the first laser light L1 from the first electrode 11 side, and processing for improving the light emission luminance is performed.

  The first laser beam L1 as the light emitting layer absorption side laser beam irradiated to the light emitting layer 13 has a wavelength at which the absorption rate of the single layer of the light emitting layer 13 is 40% or more. In this case, the wavelength is 355 nm.

  Further, the second laser beam L2 as the electrode absorption side laser beam irradiated to the first electrode 11 has a wavelength at which the absorption rate of the first electrode 11 in the single film is 30% or more. In FIG. 1, the wavelength is 532 nm.

  As described above, in the EL element, laser light can be transmitted from one or both of the pair of electrodes 11 and 15 to the light emitting layer 13. In the EL element 100 of this example, the laser light is transmitted. Can be transmitted from both the electrodes 11 and 15 side.

  Here, in this example, like a normal EL element, the pair of electrodes 11 and 15 are formed of the same material, that is, ITO, and have different film thicknesses. In such a case, the second electrode 15 having a smaller thickness is more likely to transmit laser light, and the first electrode 11 having a larger thickness is more likely to be absorbed. In the case of this example, the absorptance in the thin second electrode 15 and the second insulating layer 14 at the wavelength of the first laser beam L1 is 30% or less, and 70% of the first laser beam L1. The above can be absorbed by the light emitting layer 13.

  Therefore, in this example, as shown in FIG. 1, the irradiation with the first laser light L1 to be absorbed by the light emitting layer 13 is performed from the second electrode 15 side having a small thickness (200 nm), Irradiation with the second laser beam L2 to be absorbed by the first electrode 11 is performed from the thick first electrode 11 side, that is, from the outside of the glass substrate 10.

  As a laser irradiation apparatus in this laser irradiation step, a known apparatus can be adopted, and FIG. 2 shows an example of the apparatus as a schematic configuration.

  This apparatus emits laser beams L 1 and L 2, a homogenizer 202 that adjusts and optimizes the waveforms of the laser beams L 1 and L 2 emitted from the laser oscillator 200, and laser beams L 1 and L 2 from the homogenizer 202. A condensing lens 204 for condensing the EL element 100 and reflecting mirrors 201 and 203 that are provided between these members and transmit laser beams L1 and L2 are provided.

  As the laser oscillator 200, a generally used solid-state laser using a semiconductor or an excimer laser using a gas can be used. As is well known, changing the wavelengths of the laser beams L1 and L2 emitted from the laser oscillator 200 is realized by changing the type of laser.

  Here, both the first laser beam L1 having a wavelength of 355 nm (third harmonic) and the second laser beam L2 having a wavelength of 532 nm (second harmonic) are emitted from one laser oscillator 200. Laser light having a wavelength is emitted. Although not shown, two oscillators that can oscillate the first laser beam L1 having a wavelength of 355 nm and two oscillators that can oscillate the second laser beam L2 having a wavelength of 532 nm may be used.

  Then, the laser beams L 1 and L 2 emitted from the emission port of the laser oscillator 200 are sent to the homogenizer 202 via the reflection mirror 201. With this homogenizer 202, each of the laser beams L1 and L2 is formed in a top hat beam shape, condensed by a condensing lens 204 via a reflection mirror 203, and shaped into a beam size of a desired size. Are simultaneously irradiated.

  In the present embodiment, in order to improve the light emission luminance, the first laser light L1 is assumed to have a wavelength at which the absorption rate of the single layer of the light emitting layer 13 is 40% or more, and the second laser light L2 is The basis for the fact that the absorption rate in the single film of the first electrode 11 has a wavelength of 30% or more will be described.

  The inventor investigated the absorption rate of laser light in a single film state for each of the light emitting layer 13 and the first electrode 11 in the EL element 100 of the above-described example. The results are shown in FIGS.

  FIG. 3 is a diagram showing the relationship between the wavelength of laser light (unit: nm) and the absorptance (%) of a single layer of the light emitting layer 13, and FIG. 4 shows the relationship between the wavelength of laser light (unit: nm) and It is a figure which shows the relationship with the absorptivity (%) in the single film of the 1st electrode.

  As shown in FIGS. 3 and 4, the absorptance in each of the films 11 and 13 is changed by changing the wavelength of the laser beam. Regarding the brightness improvement by laser irradiation, the detailed mechanism has been unknown, but it has been estimated that the energy of the laser beam has some positive influence on the light emitting layer that is the object to be irradiated.

  Therefore, if the present inventor uses a laser beam having a wavelength with a large absorption rate, the laser beam energy is given to the irradiated object. Therefore, the absorption rate of each of the laser beams L1 and L2 is changed to change the above figure. As shown in FIG. 1, the laser irradiation process was performed, and the effect of improving the luminance was investigated.

  Specifically, the absorption rate (%) of the light emitting layer absorption side laser beam, that is, the first laser beam L1, in the light emitting layer 13, and the absorption of the electrode absorption side laser beam, that is, the second laser beam L2, at the first electrode 11 are as follows. The luminance ratio when the rate (%) was changed was investigated.

  The results are shown in FIGS. 5 shows the absorption rate of the light emitting layer absorption side laser light in the light emitting layer 13 on the horizontal axis and the luminance ratio on the vertical axis. FIG. 6 shows the absorption of the electrode absorption side laser light at the first electrode 11. The horizontal axis represents the rate and the vertical axis represents the luminance ratio.

  Here, the luminance ratio indicates the luminance after the laser irradiation step when the luminance is measured before and after the laser irradiation step under the same driving conditions, and the luminance before the laser irradiation step is normalized to 1. As the luminance ratio is larger than 1, the luminance is improved by laser irradiation.

  In FIGS. 5 and 6, the absorption rate of the light emitting layer absorption side laser beam (first laser beam) L1 in the light emitting layer 13 is changed to 35%, 40%, 45%, and 98%. The wavelengths corresponding to these absorptances are 532 nm, 355 nm, 351 nm, and 308 nm, respectively, from the relationship diagram shown in FIG.

  On the other hand, in FIGS. 5 and 6, the absorption rate of the electrode absorption side laser beam (second laser beam) L2 at the first electrode 11 is changed to 25%, 30%, 40%, and 80%. The wavelengths corresponding to these absorptances are 511, 532 nm, 355 nm, and 308 nm, respectively, from the relationship diagram shown in FIG.

  As shown in FIGS. 5 and 6, it was confirmed that the luminance ratio increases as the absorption rate of each of the laser beams L1 and L2 increases, and the luminance improvement effect tends to increase as the absorption rate increases. .

  If the absorption rate of the first laser beam L1 in the light emitting layer 13 is 40% or more and the absorption rate of the second laser beam L2 in the first electrode 11 is 30% or more, the luminance ratio is It has been found that the luminance is improved and the luminance is improved.

  From FIGS. 5 and 6, the absorption rate of the first laser beam L1 in the light emitting layer 13 is 35% or the absorption rate of the second laser beam L2 in the first electrode 11 is 25%. Although some improvement in luminance is observed, the absorption rate of the first laser beam L1 in the light-emitting layer 13 is 40% or more in order to ensure stable improvement in consideration of manufacturing errors and the like. In addition, it is desirable that the absorption rate of the second laser beam L2 at the first electrode 11 is 30% or more.

  The same tendency as that shown in FIGS. 5 and 6 has been confirmed in the device having the element configuration of this embodiment. Based on this, in the present embodiment, the first laser light L1 is assumed to have a wavelength at which the absorption rate of the single layer of the light emitting layer 13 is 40% or more, and the second laser light L2 is The absorption rate of the first electrode 11 in the single film has a wavelength of 30% or more.

  In this embodiment, by performing the laser irradiation process using such laser beams L1 and L2, the light emitting layer 13 is sandwiched between the pair of electrodes 11 and 15, and then the laser irradiation is performed to improve the luminance. Can do.

  Further, the first laser beam L1 has a wavelength such that the absorption rate of the single layer of the light emitting layer 13 is 40% or more, and the second laser beam L2 is absorbed by the single layer of the first electrode 11. The wavelength is assumed to have a wavelength of 30% or more, but not strictly 40% or more, 30% or more, and may have a certain width within an equal range.

(Second Embodiment)
FIG. 7 is a diagram showing a schematic cross-sectional configuration of an EL element 200 according to the second embodiment of the present invention.

  In the first embodiment, the first electrode 11 is thicker than the second electrode 15, but the EL element 200 of the present embodiment is contrary to the second electrode 15. Is thicker than the first electrode 11. Specifically, the thickness of the second electrode 15 is 600 nm, and the thickness of the first electrode 11 is 200 nm.

  In this case, as shown in FIG. 7, the irradiation with the first laser beam L1 to be absorbed by the light emitting layer 13 is performed from the side of the first electrode 11 having a small thickness, and the second laser beam L2 is irradiated. Irradiation is performed from the thick second electrode 15 side. The second laser light L2 has a wavelength at which the absorption rate of the second electrode 15 in the single film is 30% or more, and the wavelength can be selected from FIG.

  Since these are the same as those in the above embodiment, the same effects as those in the above embodiment can be obtained by this embodiment.

(Other embodiments)
The first laser beam L1 and the second laser beam L2 each have a wavelength with an absorption rate of 40% or more in the single layer of the light-emitting layer 13, and the single electrodes 11 and 15 to be absorbed. As long as the absorption rate in the film has a wavelength of 30% or more, the first laser light L1 and the second laser light L2 may have the same wavelength.

  Further, the irradiation with the first laser beam L1 and the irradiation with the second laser beam L2 do not have to be performed at the same time. After one irradiation is performed, the other irradiation is performed in order. You may go.

  Moreover, in the said embodiment, although both of a pair of electrodes 11 and 15 consisted of ITO, the material of one electrode and the other electrode may differ. For example, as shown in FIG. 8, the first electrode 11 may be ITO, and the second electrode 15 may be a metal electrode made of Al.

  In this case, the laser light can be transmitted from the first electrode 11 made of ITO to the light emitting layer 13, but is not transmitted to the light emitting layer 13 from the second electrode 15 that is a metal electrode.

  Therefore, the first laser beam L1 may be irradiated from the first electrode 11 side to the light emitting layer 13, and the second laser beam L2 may be irradiated from the second electrode 15 side to be absorbed by the second electrode 15. .

  Even when a metal electrode is used, if the relationship between the wavelength of the laser beam as described above and the absorptance of the metal electrode in a single film is obtained, the wavelength of the second laser beam L2 applied to the metal electrode can be determined. I can decide.

  Further, it is necessary that laser light can be transmitted from at least one of the pair of electrodes 11 and 15 to the light emitting layer 13, and in this respect, the pair of electrodes 11 and 15 are formed of different materials. In this case, it is preferable that either one of the electrodes is ITO.

  Moreover, each electrode, the light emitting layer, and the insulating layer described above show one embodiment, and are not limited to the above examples.

  For example, as the base material of the light emitting layer, there are SrS, CaS and the like in addition to ZnS. Usually, the light emitting layer material used for EL depends on the film forming method, but all have the same band gap. Therefore, it is considered that the effect of improving the luminance due to the application of the laser energy is similarly exhibited.

  In addition, the EL element that employs the laser irradiation method is not limited to the inorganic EL, and may be an organic EL element that uses an organic material as a light-emitting layer if possible. An example of a cross-sectional configuration of the organic EL element is shown in FIG.

  An anode 11 as a first electrode made of a transparent conductive film such as ITO is formed on the transparent substrate 10 on the light extraction side, and an organic layer 13 as a light emitting layer is formed on the anode 11. .

  Actually, the organic layer 13 is a laminate including a light emitting layer in which a hole transport layer, a light emitting layer, an electron transport layer, and the like are laminated. On the organic layer 13, a cathode 15 is formed as a second electrode made of a metal electrode such as Al.

  In addition, such an organic EL element is formed by forming the above films 11, 13, and 15 on the substrate 10 by sputtering or vapor deposition, and then sealing each film with a glass cover 20 to cause deterioration due to intrusion of moisture or the like. Is preventing.

  In such an organic EL element, after the glass cover 20 is assembled, the first laser light L1 is irradiated from the transparent anode 11 side to the light emitting layer 13, and the second laser is emitted from the cathode 15 side through the glass cover 20. What is necessary is just to irradiate the light L2 and to make this absorb in the cathode 15. FIG.

It is a schematic sectional drawing of the EL element which concerns on 1st Embodiment of this invention. It is a figure which shows typically the example of 1 structure of the laser irradiation apparatus which concerns on the said 1st Embodiment. It is a figure which shows the relationship between the wavelength of a laser beam, and the absorption factor in the single film | membrane of a light emitting layer. It is a figure which shows the relationship between the wavelength (unit: nm) of a laser beam, and the absorption factor (%) in the single film | membrane of a 1st electrode. It is a figure which shows the change of a luminance ratio when changing the absorption factor in the single film of the light emitting layer of the 1st laser beam, and the absorption factor in the single film of the 1st electrode of the 2nd laser beam. It is a figure which shows the change of a luminance ratio when changing the absorption factor in the single film of the light emitting layer of the 1st laser beam, and the absorption factor in the single film of the 1st electrode of the 2nd laser beam. It is a schematic sectional drawing of the EL element which concerns on 2nd Embodiment of this invention. It is a schematic sectional drawing which shows the EL element which used one side of a pair of electrode as a metal electrode as other embodiment of this invention. It is a schematic sectional drawing of an organic EL element.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Board | substrate, 11 ... 1st electrode, 13 ... Light emitting layer, 15 ... 2nd electrode,
L1 ... 1st laser beam, L2 ... 2nd laser beam.

Claims (3)

A light emitting layer (13) containing a light emitting substance is sandwiched between a pair of electrodes (11, 15), and laser light is transmitted from at least one of the pair of electrodes (11, 15) to the light emitting layer (13). Is a method of manufacturing an EL element through which is transmitted,
After the light emitting layer (13) is sandwiched between the pair of electrodes (11, 15), the first light having a wavelength at which the absorption rate of the single layer of the light emitting layer (13) from the one electrode side is 40% or more. The laser light (L1) is irradiated onto the light emitting layer (13), and the absorptivity of the other electrode from the other electrode side opposite to the one electrode is 30% or more. A method for manufacturing an EL element, comprising: irradiating the other electrode with a second laser beam (L2) having a wavelength of ## EQU2 ## to improve emission luminance. 2. The method of manufacturing an EL element according to claim 1, wherein the irradiation with the first laser beam (L1) and the irradiation with the second laser beam (L2) are performed simultaneously. The pair of electrodes (11, 15) are formed of the same material and have different film thicknesses.
Irradiation of the first laser beam (L1) is performed from the electrode having the smaller film thickness, and irradiation of the second laser beam (L2) is performed from the electrode having the larger film thickness. The manufacturing method of the EL element of Claim 1 or 2.

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